The diagnosis of mental illnesses is initially based primarily on conversations that explore the patient’s experiences and feelings (the doctor says explore):
In addition, the therapist uses observations of the patient, questionnaires and psychological tests (02.10.2022):
https://www.apotheken.de/krankheiten/hintergrundwissen/4655-der-weg-zur-diagnose-in-der-psychiatrie
Peter Gamma from www.petergamma.or does not know of psychiatrists who treat their patients with brain scanners in Switzerland. But in Spain, prisoners’ brains are being electrically stimulated in the name of science: